1. Field of the Invention
This invention relates to central office protector modules which provide an indication when either of the lines protected by the module are shorted to ground and more particularly to a telephone distribution frame connector assembly for use therewith.
2. Description of the Prior Art
Telephone distribution frame connectors, or panels as they are sometimes called, of the type having plug-in modules are generally known in the telephone art. In such connectors outside lines are connected to in-plant or central office switching equipment through protector modules which protect the inside equipment from damage due to overvoltage or overcurrent faults. These connectors or panels are mounted on distribution frames which are generally positioned close together. Space is often at a premium in such installations and accordingly, down-sizing or other space saving measures in the design of the connector assembly is a continuing objective.
A typical such connector assembly includes a module field which includes suitable connectors and terminals for receiving a plurality of overload protectors, a test field for receiving a test shoe to test the integrity of the connections, and an equipment field for terminating conductors from the inside plant equipment or central office switching equipment. The incoming lines are generally terminated either directly or through a cable stub to the terminals of the module field, which are respectively coupled to the appropriate terminals of receptacles which receive the respective overload protector modules. In this regard, a protector module is provided for each line pair being terminated in the module field. Accordingly, the protector modules are coupled between the incoming lines and the equipment field to provide a surge path to ground for the respective lines when an overvoltage fault or a current surge appears. In addition, the test field comprises a series of terminals coupled to the respective incoming lines. Thus, the connector assembly provides a protected interface between the incoming lines and inside plant lines and equipment, as well as providing a convenient place to test the various lines.
One example of such a connector assembly which meets current telephone operating requirements for minimizing connector assembly size and increasing protector module density is the R399 type assembly sold by assignee's Reliable Electric/Utility Products operating unit. A detailed description of that assembly may be obtained by referring to allowed U.S. patent application Ser. No. 008,055 entitled "Access Panel and Fanning Strip For Telephone Distribution Frame Connector Assembly" filed on Jan. 16, 1987 (now U.S. Pat. No. 4,752,249 which issued on June 21, 1988) which is assigned to the same assignee as is the present invention. A partial description of that assembly is given herein using several of the drawing figures and reference numerals used in the above identified application.
Referring now to FIG. 1 and FIG. 2, there is shown the above identified prior art connector assembly designated generally by the reference numeral 20. This assembly comprises a generally C-shaped frame member 22 which supports or mounts the remaining components of the assembly. In this regard, a module field block 24 mounts at an outer side thereof a plurality of prior art overvoltage or surge protector modules 25 which do not include the alarm indicator of the present invention. As will be seen later, each of these modules 25 receives an outside line and a corresponding line pair from inside telephone equipment or the like and provides a surge or discharge path to ground to protect the inside equipment from overvoltage or sudden current surges on the outside lines.
A test field block 26 and an equipment field block 28 are mounted in side-by-side condition to the frame member 22 and together define the front side of the assembly. A rear side of assembly is defined generally by a rear wall portion 27 of the frame member 22. This wall 27 supports outwardly extending ears or tabs 29 which may be utilized to mount suitable clamps 30 for receiving an incoming cable or cable stub 31. Others of these ears or tabs 29 are used to mount the entire assembly 20 to a telephone distribution frame (not shown), which receives a plurality of similar connector assemblies to form a distribution system.
In this regard, and referring also to FIG. 2, it will be seen that the module field block 24 includes receptacles 32 to mount or receive the protector modules 25. The opposite or inner side is provided with a plurality of terminals 54 corresponding respectively to the terminals of the modules 25, and is generally referred to in the art as the "back plane". The module field block also defines an upstanding peripheral wall portion 34 which surrounds the modules 25 on four sides. The modules 25 may be removed and inserted with respect to receptacles 32 by grasping outer ends 36 thereof as illustrated for the module 25a. It will be noted that the front side of the raised peripheral wall 32 of the module field block 24 is provided with an integral extension 38 which flares outwardly at generally a right-angle to form a side wall portion 40, further defining a portion of the left-hand side of the assembly 20. This side wall 40 terminates at an edge 42. A corresponding outwardly projecting shoulder portion or edge 44 of the test field block 26 abuts and overlies this edge 42.
It will also be noted that the module field block 24 also includes an additional or rear wall portion 46 which generally forms an extension of the rear portion of upstanding wall portion 34 and thus forms a rear wall of the assembly 20. It will be seen that the assembly thus far described generally defines an enclosure, with test field block 26 and equipment field block 28 forming a front side thereof, and module field block 24 forming a left-hand and rear side thereof. The top and bottom of this enclosure are defined respectively by symmetrical upper and lower side portions 39, 41 of the C-shaped frame member 22. In this regard, the upper side portion 39 is best viewed in FIG. 1, it being understood that the lower side portion 41 is substantially a mirror image thereof. The last, otherwise open, right side is normally covered by an access panel 48.
As previously indicated, each of the field blocks 24, 26 and 28 includes a plurality of terminals or connector members on an outer surface for receiving conductors or mating connectors. In this regard, the modules 25 mate with the connectors carried in the receptacles 32 of module field block 24.
Outside lines enter from the cable or stub 31 by way of a plurality of through aligned openings 50, 52 defined respectively in the rear side of the frame member 22, as best seen in FIG. 3. In this regard, it will be noted that the rear portion 27 of the frame member 22 overlies a major portion of the rear wall 46 of the module field block 24. Preferably, the openings 52 include raised peripheral lip portions 53 to facilitate alignment of the module field block with the frame. This arrangement also holds wires running therethrough away from the metal frame, to avoid possible abrasion or damage to the wires by the edges of the openings 50 of the metal frame.
As previously mentioned, these outside lines are connected to in-plant or central office switching equipment through the protector modules 25, and these connections are accomplished at selected terminals of the back plane, as designated generally by reference numeral 54. In this regard, additional terminals for the back plane wiring are also defined on the interior sides of the test field block 26 and the equipment field block 28, these latter terminals being respectively designated by general reference numerals 56 and 58.
In operation, the wiring is then carried from others of the terminals 54 to the desired terminals 58 of the equipment field block 28, the connections thereof to inside equipment being completed at the outer face thereof which bears corresponding terminals indicated generally by reference numeral 60. The terminals 56 of the test field block 26 are generally coupled to those terminals 54 which receive the incoming lines to permit a convenient place to test these various lines. In this regard, a suitable complementary test shoe (not shown) may be interfitted over the exterior of the test field block 26 to accomplish such testing.
It will be noted that the frame member top and bottom wall portions 39 and 41 overlie the top and bottom edge portions of panel 48 to complete the enclosure, these latter walls 39 and 41 being of relatively rigid metallic material, thereby insuring the integrity of the enclosure thus formed. In this regard, it will also be noted that the module field block 24, test field block 26 and equipment field block 28, as well as access panel 48 and hold-down strip 70 are all preferably formed, as by molding, from a suitable nonconductive material and preferably a relatively rigid and moldable plastic material.
Referring now to FIGS. 4 through 6 inclusive, the grounding arrangement for the connector assembly will next be described. Initially referring to FIG. 5, it will be seen that each of the protector modules 25 carries, at a bottom portion thereof, a plurality of terminal members. A first pair of these terminals 98 are for receiving an incoming line pair, while a second pair 100 are for receiving a corresponding line pair from the inside equipment. The remaining terminal 102 is designated as the ground terminal, through which any overvoltage or current surge condition is to be discharged or dissipated. Accordingly, and referring to FIG. 4, the rear or back plane side of module field block 24 includes corresponding groups of five terminals each which are here designated by like reference numerals 98, 100, 102, together with the respective suffixes a, b and c.
Advantageously, a ground bus means or system is provided for electrically interconnecting all of these ground terminals which are located interiorally of the enclosure defined by the assembled connector assembly, 20, that is, in the back plane 54. In the illustrated embodiment, the ground bus system includes a first, generally centrally disposed bus member or bus bar 104 of a predetermined cross-section, preferably equivalent to No. 6 AWG copper alloy solid wire size. This central conductor or ground bus 104 will be seen to run vertically and be generally centered with respect to the ground plane 54. The module field block 24 is preferably provided with a corresponding groove or slot 106 (see FIG. 6) to receive the first bus bar 104. This bus bar 104 is provided with a plurality of generally circular slots or openings 107 in its upper surface which in turn receive generally cylindrical bus bars or conductive rods 108.
These latter bus bars or conductive rods 108 are coupled directly to respective ground terminals 102a, 102b, etc., as by soldering as indicated, for example, generally at 110. These latter bus bars 108 are preferably No. 12 AWG copper alloy solid conductors. It will be noted with reference to FIG. 3 that a total of ten protector modules 25 are arranged in each horizontal row. Accordingly, and as required by industry standards, no more than five of these ground terminals 102a etc. are coupled to any given bus bar 108 before its junction with the larger center bus member 104. In this regard, the bars 108 are further coupled with the slots 107 which are formed to receive them in the rectangular center bus 104 by suitable means as by soldering as indicated generally at 112.
Advantageously, the ground bus system is carried exteriorally of the housing for grounding with the frame 22, which it will be remembered is mounted to a main distribution frame, which comprises what is known in the art as a "frame ground". Alternatively, as can be seen by referring to the above referenced patent application, a ground selecting means or assembly of the connector assembly permits the connector ground to be carried to some ground other than, or isolated from, this frame ground or what is generally known in the art as an "isolated ground".
Referring again to FIGS. 4 and 6, an additional bus bar member 114 is provided for carrying this ground connection exteriorally of the housing or enclosure defined by the assembled connector assembly. This latter bus bar 114 is also preferably equivalent in cross-section to No. 6 AWG copper alloy solid wire size. A groove or channel 115 is provided in the module field block 24 to receive this second bus bar 114. Advantageously, it is relatively simply interfitted with the similarly dimensioned center bus bar 104 by providing identical slots in each of the bus bars 104 and 114 in a substantially "T-shaped" configuration, this junction being indicated generally by reference numeral 116 in FIG. 4 and in FIG. 6. Additionally, this connection may be further secured as by soldering as also indicated at 118 in FIG. 4.
There has been increasing demand for a central office protector module which provides an indication when the module shorts either of the two lines protected by the module to ground. One example of such a module is that shown in U.S. Pat. No. 3,587,021 entitled "Line Protector For A Communications Circuit" which issued on June 22, 1971 and is assigned to the same assignee as is the present invention. The module shown therein includes a sixth or alarm pin which is connected to ground when a sustained overcurrent condition causes the module to ground either of the two lines protected by the module. Such a module is sold by assignee's Reliable Electric/Utility Products operating unit as the type R1104B module. That module plugs into a type 700 connector also sold by that same operating unit.
The type R1104B module while providing a visual indication of failure due to a sustained overcurrent condition does not provide a visual indication of failure due to a sustained overvoltage condition. In addition, the type 700 connectors are much larger and have a much smaller module density than frame connector assemblies of the R399 type. Therefore, operating companies have been expressing demand for a module which provides not only a visual indication when the module connects at least one of the two lines it is protecting to ground due to a sustained overcurrent or overvoltage condition, but also that a frame connector assembly having the size and increased module density of the R399 type assembly be useable with such modules.